207 
certain Varietal and Hybrid Ferns. 
be regarded as approximately representing the position of the lines of force 
in a magnetic field between such unlike poles. Gallardo , 1 on the con¬ 
trary, has argued that the difficulties that must underlie the assumption 
of unlike poles under the conditions in which they could exist in the cell 
are wellnigh insuperable. It is difficult to see how they could be kept 
asunder, much less to understand how they could actually move still further 
apart . 2 Gallardo’s contention is that the apices of the spindle represent not 
unlike but like poles, and he regards them as due to an inductive effect, 
dependent on the charge carried by the contents of the nucleus. At the same 
time he remarks that there are cases in which the achromatic fibres are 
entirely differentiated in the cytoplasm under conditions in which the nu¬ 
cleus is excluded from all share in the process. Such an example is afforded 
when, by the agency of drugs, the spindle fibres are caused to appear in cells 
from which the nucleus has been removed. In this case Gallardo thinks 
that the poles are really unlike . 3 
It seems improbable that there can exist so fundamental a difference 
in this respect, and we are ourselves of opinion that the solution of the 
problem will be found to lie in the proof that the poles are always similar 
to each other and of opposite sign to that of the acid nucleus. The 
matter is complicated by the colloidal nature of the material in which the 
process is going on, and the state of lag, so well insisted on by Hartog, 
may well account for much that is otherwise anomalous. We recognize 
that the so-called ‘Hermann’s Spindle’, as well as those other instances 
in which the centrosomes diverge from each other, although the connecting 
fibres form a convergent system of curves, are difficult cases. But the re¬ 
markable manner in which the sheaves of fibres in these ferns diverge from 
the proximity of the chromatin-charged linin, and are so repelled by each 
other that they press out equidistantly at the periphery of the cytoplasm, 
seems to us to provide an almost overwhelming support for the hypothesis 
that the linin with its contained chromatin, by virtue of the chemical changes 
involved in its metabolism, has brought about an electrical condition of 
opposite sign similar in each of the spindle-cones formed from the substance of 
which the kinoplasm is made up. This hypothesis also is in harmony with 
the fact that the disappearance of the nuclear membrane is closely as¬ 
sociated with the spreading of the chromosomes beneath it just before 
their retrogressive movement to the equator, whilst the spindle poles have 
shifted away from the nuclear surface. The change of size of the nucleus, 
1 Gallardo, A., L’interprdtation bipolaire de la division karyocinetique. An. Mus. Nac. de 
Buenos Aires, t. xiii. 
2 The subsidiary hypotheses which have been advanced to explain the spindle mechanism on the 
assumption of unlike poles do not appear to us to be convincing. 
3 In a paper just published in the Archiv f. Entwickelungsmechanik (vol. xxviii) Gallardo has 
given up this view, and asserts that the sign is always similar in the cytoplasm, i. e. electropositive. 
